The present invention relates to a monitor unit for a vehicle seat, which is attached to the top portion of the seat back of a vehicle seat, and whose display surface is directed to the rear of the vehicle during use.
A monitor unit of this type is disclosed in U.S. Pat. No. 6,698,832. This monitor unit includes a base portion installed at a top of a seat back and a monitor portion building therein a monitor with its display surface exposed to an exterior. The monitor portion is pivotally connected to the base portion via a hinge, and is rotatable in a front/rear direction of the vehicle between a use position (in which it is kept erect on the base portion, with its display surface being directed to a rear of the vehicle), and a retracted position (in which it has been tilted toward a front side of the vehicle around the hinge). In the use position, the monitor portion is situated on a rear surface of a headrest, with the display surface being directed to the rear of the vehicle. When placing the unit in the retracted position, the headrest is detached from the seat back, and the monitor portion is tilted toward the front side of the vehicle by 90 degrees around the hinge, which is arranged at the rear end of the base portion. In the retracted position, the monitor portion is laid horizontally on the base portion. The monitor portion includes a housing portion surrounding an outer periphery of the monitor, with the display surface being exposed, and a support portion provided upright on the base portion and supporting the monitor within a housing portion on both right and left sides thereof. Hinges are provided at right and left top portions of the support portion, and a substantially middle portion in a vertical direction of the housing portion is pivoted to the support portion via the hinges. The angle of the housing portion can be adjusted with respect to the support portion using the hinges at the top of the support portion as rotation shafts thereof.
However, in the retracted position of the monitor unit, the monitor portion is simply tilted by 90 degrees. This means that the monitor portion is on the base portion even in the retracted position, so a thickness of the monitor portion constitutes an obstruction. At the same time, an upper portion of the monitor portion protrudes to the front side of the seat back. As a result, an amount by which the monitor portion protrudes to the front side of the seat back increases as a height of the monitor portion increases, which also leads to an obstruction. A way to solve this problem would be to reduce thickness and height dimensions of the monitor portion. However, from a technical viewpoint, there is a limitation to a reduction in thickness of the monitor portion. A reduction in height dimension of the monitor portion results in a reduction in an area of the monitor display surface, making an image displayed rather hard to see. To begin with, as long as the monitor portion is laid flat on the base portion in the retracted state, no radical solution of the problem will be possible.
Further, the right and left side portions of an interior of the housing portion which constitutes the monitor portion are rotatably supported by the support portion via the hinges. As a result, the width dimension of the housing portion must be at least not less than the dimension by which the support portion having the hinges protrudes outwardly to the right and left from the monitor. When considered in relation to the headrest, there is a limitation to the size of the monitor unit as a whole, so when the width dimension of the housing portion increases, the area of the display surface of the monitor becomes much smaller. Further, when adjusting the angle of the housing portion, there is generated a gap between the housing portion and the base portion, and no member is provided in particular for a purpose of covering this gap. This leads to a rather poor outward appearance, an easy intrusion of dust, and a fear of the fingers of an operator to be caught during rotating operation. At the same time, an upper portion of the housing portion is displaced to the front side of the vehicle where the headrest exists. Thus, it is necessary to provide within the headrest a space at least corresponding to a displacement of the upper portion of the housing portion, resulting in a reduction in degree of freedom in terms of a design of the headrest.
Apart from this, examples of a monitor unit to be arranged on the back surface of a seat back or a headrest, with its display surface being directed to the rear of the vehicle, are disclosed in JP 2002-2395 A and JP 2005-251367 A. In those examples, the monitor portion is rotatably supported so as to allow angle adjustment with respect to a support portion; however, there is no mechanism allowing displacement between the use position and the retracted position.